First of all, I love the spelling Cecelia, even though it isn't the "proper" spelling. I like it that way to make it easier to have the nn Celia and to get away from the name Cecil.
My vote was for Cordelia though. It's not as common. I really dislike Delia, which is funny cuz I like Celia, but I like do like Cordy. Cordy would be cute on a child. I like the full name Cordelia and I prefer full names. Cecelia as a full name seems like it would always be shortened to Cece or Celia.